Abstract
Previously regarded as an obscure disorder, nonalcoholic steatohepatitis (NASH) has recently emerged as an important chronic liver disease. NASH is within a spectrum of disorders characterized by excessive accumulation of fat in the liver, including simple hepatic steatosis (fatty liver), inflammation and necrosis (steatohepatitis), and fibrosis. Collectively, the disorders are called nonalcoholic fatty liver disease (NAFLD). Estimates of the prevalence of these individual conditions are suspect because liver biopsy is required for definitive diagnosis and is not generally performed. Although these conditions have traditionally been thought of as diseases of obese women, and are frequently associated with diabetes mellitus and hypertriglyceridemia, they have also been identified in lean men. Insulin resistance appears to be a common factor. These conditions are difficult to distinguish from each other clinically, and no biochemical or radiological test reliably establishes the diagnosis. A ratio of serum aspartate to alanine aminotransferase levels of less than one can distinguish NAFLD from alcoholic liver disease, but this is a nonspecific finding. Fatty infiltration imparts a diffuse echogenicity to the liver at ultrasonography, but this test cannot easily distinguish fat from fibrous tissue or identify cases of NASH. Only histological examination can establish the diagnosis of NASH, grade its severity, determine the prognosis and guide treatment.